X-Ray systems, such as digital radiographic imaging systems, comprise an x-ray tube or source and a detector. The source is moveably mounted to a mounting structure such as a wall or ceiling in an examination room, and the detector is provided on a horizontal table or vertical stand. Typically, the detector mounting structures are also moveable in at least one direction.
In a typical setup, the source is mounted to a rail provided on the ceiling the X-ray room, and the detector or digital wall stand is provided on a stand positioned against a wall of the room. The source is moveable in longitudinal, latitudinal, and vertical directions, and may also be rotationally moved to a number of angular positions. The detector can also be moveable, typically in a latitudinal and vertical direction. Due to the large variety of possible positions, the medical imaging system is calibrated on start up such that, based on feedback, it can be determined that the source is directed at a lateral and vertical center of the detector at a known source to image distance (SID).
The installation and setup procedure for typical prior art digital imaging systems, such as digital radiographic imaging systems, are both complex and time-consuming. To comply with customer image quality and consistency requirements and various regulatory and safety standards, typical procedures require the determination of a variety of constants including fixed setpoints for laterally centering the x-ray source with respect to the center of the detector and the establishment of fixed setpoints (or detent positions) for setting the separation distance between the x-ray source and x-ray detector and calibrating the system such that an accurate readout of the separation distance can be obtained. The determination and establishment of this separation distance, referred to as the source-to-image distance (SID), assists in appropriately controlling the size of the x-ray field during diagnostic use of the imaging system. Further, many regulatory requirements specify that the SID must be clearly displayed to the operator or user of the system with a certain level of accuracy.
More recently, automated methods for establishing lateral and vertical center points of the detector have been developed. These provide an improvement over prior art methods by eliminating the need for a number of “hard” stops and detent locations, instead providing flexibility in moving the source with respect to the detector.
While each of these method of calibration are perfectly acceptable if the mechanical linkages and the mounting locations are straight, there are often irregularities in each. Therefore, as the source is moved from a calibrated position to a non-calibrated position, an offset can be induced between the expected position, and the actual position of the device. For example, in an examination room, the relative distance between the floor and the ceiling may differ across the room. Therefore, when either the X-ray source or detector is moved even in what appears to be a straight line, the source can become misaligned with the detector, resulting in an image in which the field of view is not appropriately positioned on the patient. In this case, the resultant images can be inaccurately placed or cropped, such that the portion of the anatomy sought to be imaged can be lost.
Thus, it would be desirable to provide a system for installing and calibrating a digital radiographic or other imaging system which would account for variations in the surrounding room structure when the source and detector components of the system are repositioned.